IGP Extensions for Advertising Link NumbersFutureweiBoston, MAUSAhchen.ietf@gmail.comFuturewei2386 Panoramic CircleApopka, FL32703USA+1-508-333-2270d3e3e3@gmail.comChina TelecomBeiqijia Town, Changping DistrictBeijing102209Chinawangaj3@chinatelecom.cnVerizon Inc.13101 Columbia PikeSilver SpringMD 20904USA 301 502-1347gyan.s.mishra@verizon.comChina Mobileliuyisong@chinamobile.comCasa SystemsUSAyfan@casa-systems.comFujitsuUSAliulei.kddi@gmail.comAlef Edge USAxufeng.liu.ietf@gmail.comThis document describes OSPF and IS-IS extensions for distributing
the link numbers assigned to the links originating at a node.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in
when, and only when, they appear in all capitals, as shown here.When the links originating at each node in a network are numbered
from 1 to the
number of the such links for that node, an efficient stateless multicast along
an explicit P2MP path can be achieved through using
the link numbers of the links on the path to represent the path.This document proposes OSPF and IS-IS extensions for distributing
the link numbers assigned to the links originating at a node
which will support such multicast.
After a controller such as PCE as a controller has the
link numbers of the links originating at every node,
for an explicit P2MP path, the controller
can send the ingress the path represented by the link numbers
of the links on the path.Link State Advertisement.Open Shortest Path First.Link State Protocol data unit.Intermediate System to Intermediate System.Multi-Topology.Traffic Engineering.This section describes extensions to OSPFv2 for distributing
the link numbers assigned to the links of a node. defines the OSPFv2 Extended Link TLV
to advertise the information about a link.
Multiple Link TLVs for the links of a router are included
in the OSPFv2 Extended Link Opaque LSA of the router.
The OSPFv2 Extended Link TLV has the following format:
1.Variable, dependent on Sub-TLVs.
They are defined in Section A.4.2 of
.MUST be set to 0 on transmission and MUST
be ignored on reception.
Under the OSPFv2 Extended Link TLV for a link,
a Link Number Sub-TLV is
defined for distributing the link number assigned to the link
by the router originating the LSA.
A Link Number Sub-TLV is included in the Link TLV for a link of
Link Type Point-to-Point, Broadcast
(i.e., link to LAN or Transit Network), or stub (i.e., link to stub network).
The Link Number Sub-TLV has the following format:
TBD1. (Note this is the Sub-TLV Type, not the Link Type.) 2.A 2-octet field carrying the link number
assigned to the link when the Link Type of
the link in the OSPFv2 Extended Link TLV containing this Sub-TLV
is 1 (i.e., Point-to-Point connection to another router),
2 (i.e., connection to a Transit Network or LAN), or
3 (i.e., connection to a stub network).
This section describes extensions to OSPFv3
for distributing
the link numbers assigned to the links of a node. defines the OSPFv3 Extended Router LSA,
which may include multiple Router-Link TLVs.
A Router-Link TLV defines a single router link.
Under the Router-Link TLV for a link,
a Link Number Sub-TLV is defined.
This Sub-TLV has the same format as the Link Number Sub-TLV
defined above for the OSPFv2 Extended Link TLV.
The Router-Link TLV for a link
may include a Link Number Sub-TLV
for distributing the link number assigned to the link
by the router originating the LSA.
This section describes extensions to IS-IS
for distributing
the link numbers assigned to the links of a node.The Extended IS Reachability TLV (Type 22)
defined in
may contain Sub-TLVs (such as those for TE (Traffic Engineering))
that apply to a link/interface to a neighbor.
To encode multiple links or interfaces to neighbors,
the structure inside TLV is repeated.
The Multi-Topology (MT) Intermediate Systems TLV (Type 222) defined in
may contain Sub-TLVs (such as those for TE)
that apply to a link/interface.
It is aligned with the Extended IS
Reachability TLV (Type 22) but has an additional two bytes in front at
the beginning of the TLV for MT-ID.
A Link Number Sub-TLV is defined and
used in the Extended IS Reachability TLV (Type 22) and/or
MT Intermediate Systems TLV (Type 222) to
advertise the link numbers assigned to the links of a node.
The Link Number Sub-TLV has the following format:
TBD3.2.A 2-octet field carrying the link number
assigned to the link.
TBD.Under "OSPFv2 Extended Link TLV Sub-TLVs registry" as defined
in , IANA is
requested to assign a registry value for
Link Number Sub-TLV as follows:
+==============+======================+=====================+
| Value | Description | reference |
+==============+======================+=====================+
| TBD1 | Link Number | This document |
+--------------+----------------------+---------------------+
Under "OSPFv3 Extended-LSA Sub-TLVs registry" as defined
in , IANA is
requested to assign a registry value for
Link Number Sub-TLV as follows:
+==============+======================+=====================+
| Value | Description | reference |
+==============+======================+=====================+
| TBD2 | Link Number | This document |
+--------------+----------------------+---------------------+
Under "Sub-TLVs for TLVs 22, 23, 25, 141, 222, and 223"
for IS-IS TLV Codepoints, IANA is
requested to assign a codepoint for
Link Number Sub-TLV as follows:
+============+===================+==+==+==+===+===+===+=============+
|Sub-TLV Type|Sub-TLV Name |22|23|25|141|222|223|reference |
+============+===================+==+==+==+===+===+===+=============+
| TBD3 |Link Number |y |n |n | n | y | n |This document|
+------------+-------------------+--+--+--+---+---+---+-------------+
TBD.